[release-branch.go1.15] cmd/compile: do not emit an extra debug_line entry for the end of seq addr

Uses DW_LNS_advance_pc directly, instead of calling putpclcdelta
because the latter will create a new debug_line entry for the end of
sequence address.

Updates #42484.
Fixes #42521.

Change-Id: Ib6355605cac101b9bf37a3b4961ab0cee678a839
Reviewed-on: https://go-review.googlesource.com/c/go/+/268937


Trust: Than McIntosh <thanm@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/269517